1. Field of the Invention
The present invention relates to a camera shutter control device in which a shutter speed can be changed by varying the period of time from a reference time instant set in connection with a shutter releasing operation to a time instant of a shutter opening operation.
2. Description of the Prior Art
Conventionally, two types of camera focal plane shutter controls have been known, one of which is a mechanical shutter control in which a locking member of a leading curtain of a shutter is released in response to a shutter releasing operation, thereby allowing the leading curtain to run, and simultaneously a mechanical delay device is actuated so that the engagement of a trailing curtain with a locking member is released after lapse of a time manually preset by a shutter dial. The other type is of an electromagnetic shutter control in which the leading curtain locking member releases the engagement of the leading curtain in response to the releasing operation, and simultaneously a timer circuit starts measuring a time in response to a trigger signal generated in connection with the releasing operation. When the timer circuit detects a lapse of a predetermined period of time preset by a shutter dial or an automatic exposure control circuit, a signal is fed to an electric magnetic circuit provided in association with the trailing curtain, thereby releasing the engagement of the trailing curtain.
The mechanical shutter control can further be classified into two types, one of which is of the type in which a period of time from a time instant of depression of a shutter button to a time instant of releasing the trailing curtain is adjusted in accordance with a shutter speed to make constant the period of time from the time instant of depression of the shutter button to the time instant of releasing the leading curtain. The other type of the mechanical shutter control is of the type in which as disclosed in U.S. Pat. No. 4,044,368, the period of time from the time instant of depression of the shutter button to a time instant of releasing the leading curtain is adjusted in accordance with a shutter speed to make constant the period of time from the time instant of depression of the shutter button to the time instant of releasing the trailing curtain.